Gas concentrator with removable cartridge adsorbent beds

ABSTRACT

A portable oxygen concentrator designed for medical use where the sieve beds, adsorbers, are designed to be replaced by a patient. The concentrator is designed so that the beds are at least partially exposed to the outside of the system and can be easily released by a simple user-friendly mechanism. Replacement beds may be installed easily by patients, and all gas seals will function properly after installation.

RELATED APPLICATIONS

This Application is a Continuation of U.S. application Ser. No.13/066,716, file Apr. 22, 2011

FEDERALLY SPONSORED RESEARCH

Not Applicable

SEQUENCE LISTING

Not Applicable

BACKGROUND OF THE INVENTION

The invention generally relates to gas concentrators, and moreparticularly relates to medical oxygen concentrators used by patients inthe home care setting where cost and frequency of maintenance performedby a technician should be minimized.

The application of oxygen concentrators for therapeutic use is known,and many variants of such devices exist. A particularly useful class ofoxygen concentrators is designed to be portable, allowing users to moveabout and to travel for extended periods of time without the need tocarry a supply of stored oxygen or to have any maintenance performed ontheir equipment. These portable oxygen concentrators are typically inthe range of 2 to 20 lbs and produce from 0.3 to 5.0 LPM of oxygen. Mostof these portable concentrators are based on Pressure Swing Adsorption(PSA), Vacuum Pressure Swing Adsorption (VPSA), or Vacuum SwingAdsorption (VSA) designs which feed compressed air to selectiveadsorption beds. In a typical oxygen concentrator, the beds utilize azeolite adsorbent to selectively adsorb nitrogen, resulting inpressurized, oxygen-rich product gas.

The main elements in a typical portable therapeutic oxygen concentratorare shown in FIG. 1. Air is draw in, and typically filtered, at airinlet 1 before being pressurized by compressor 2 to a pressure of 1.2 to2.5 atmospheres. The pressurized air is directed by a valve arrangementthrough adsorbent beds 3. An exemplary adsorbent bed implementation,used in a concentrator design developed by the inventors, is two columnsfilled with a lithium exchanged zeolite adsorbent in the ratio of about1 gram of adsorbent per 1-10 ml of oxygen produced. The pressurized airis directed through these adsorber vessels or columns in a series ofsteps which constitute a gas separation cycle, often a PSA cycle or somevariation including vacuum instead of, or in conjunction with,compression yielding overall compression ratios of about 1.5:1 to 4.0:1.Although many different arrangements of adsorber vessels and gasseparation cycles are possible, the result is that nitrogen is removedby the adsorbent material, and the resulting oxygen rich gas is routedto a product gas storage device at 4. Some of the oxygen product gas canbe routed back through the bed to flush out (purge) the adsorbednitrogen to an exhaust 6. Generally multiple adsorbent beds, or columnsin the exemplary device, are used so at least one bed may be used tomake product while at least one other bed is being purged, ensuring acontinuous flow of product gas. The purged gas is exhausted from theconcentrator at the exhaust 6.

Such gas separation systems are known in the art, and it is appreciatedthat the gas flow control through the compressor and the adsorbent bedsis complex and requires precise timing and control of parameters such aspressure, flow rate, and temperature to attain the desired oxygenconcentration of 80% to 95% purity in the product gas stream.Accordingly, most modern concentrators also have a programmablecontroller 5, typically a microprocessor, to monitor and control thevarious operating parameters of the gas separation cycle. In particular,the controller controls the timing and operation of the various valvesused to cycle the beds through feed, purge, and pressure equalizationsteps which make up the gas separation cycle. Also present in mostportable concentrators is a conserver 7 which acts to ensure that oxygenrich gas is only delivered to a patient during inhalation. Thus, lessproduct gas is delivered than by means of a continuous flow arrangement,thereby allowing for smaller, lighter concentrator designs. A pulse ofoxygen rich air, called a bolus, is delivered in response to a detectedbreath via the conserver. Using a conserver in conjunction with a gasconcentrator may reduce the amount of oxygen required to maintainpatient oxygen saturation by a factor of about 2:1 to 9:1. A typicalconcentrator will also contain a user/data interface 8 includingelements such as an LCD display, alarm LEDs, audible buzzers, andcontrol buttons. In addition to the above subsystems, most portableoxygen concentrators contain a rechargeable battery and charging systemto power the concentrator while away from an AC or DC power source.These battery systems are typically composed of lithium ion cells andcan power the concentrator from 2-12 hours depending on the amount ofoxygen required by the patient, device efficiency, and the capacity ofthe battery pack which may range from about 40 Watt-hours to 250Watt-hours on systems with multiple battery packs.

To be practical and usable by a individual needing therapeutic oxygen,portable oxygen concentrators should be less than about 2100 cubicinches and preferably less than 600 cubic inches in total volume, lessthan about 20 pounds and preferably less than 8 pounds in weight, andproduce less than about 45 decibels of audible noise, while retainingthe capacity to produce a flow of product gas adequate to provide for apatient's oxygen needs, usually a flow rate prescribed by a medicalpractitioner in about the range of 1 LPM to 6 LPM. Further, a portablemedical oxygen concentrator must work under varied environmentalconditions such as 0° C. to 40° C. and 0%-95% relative humidity withoutcostly or frequent service or maintenance requirements. Although fixedsite PSA based concentrators have been available for many years, suchfixed site units may weigh 30-50 pounds or more, be several cubic feetin volume, and produce sound levels greater than 45 dBA. Thus portableconcentrators involve a significant amount of miniaturization, leadingto smaller, more complex designs compared to stationary units. Systemsize, weight, and complexity may lead to fewer mitigative options ordesign choices against contamination and other wear and tear effectsthat can lead to an unacceptably short maintenance interval.

One particular challenge of portable concentrator design is that theadsorbent beds must by necessity be small, yet capable of producing anadequate quantity of product gas. A portable oxygen concentrator mightrequire oxygen production of greater than 3 ml of oxygen per gram ofadsorbent in order to achieve an acceptable size of less than 600 cubicinches. Since the adsorbent beds are optimized for O₂ production pergram of adsorbent, any significant decrease in capacity of the beds overtime can result in decreased product purity as the required O₂production per gram of active adsorbent exceeds the limits of theadsorbent and PSA cycle operating parameters. One contributing factorthat can lead to a decrease in bed capacity is the adsorption ofimpurities that do not completely desorb during normal processoperation, leading to the accumulation and retention of impurities inthe beds and therefore less active adsorbent than originally intended inthe design. An example of such an impurity that reduces the adsorptioncapacity of many zeolites used in air separation is water. Somestationary concentrators utilize some means of removing water from thecompressed gas before feeding the adsorbent beds, but most rely on anexcess quantity of adsorbent to allow for contamination over time.Portable concentrators, by the nature of their application, are morelikely to be exposed to a wide range of operating conditions includinghigh humidity environments and/or rapid temperature changes that couldresult in the need for more frequent zeolite replacement. If water ispresent, either in the form of liquid (condensed out of the feedstream)or vapor, and enters the molecular sieve beds, the beds willirreversibly adsorb at least some of this water during each adsorptioncycle. The energy of adsorption of water on lithium exchanged zeolitesused in air separation is very high and not all water adsorbed duringthe adsorption steps in the process is desorbed during evacuation/purgeof the beds under typical PSA cycle operating parameters. Therefore,complete removal of adsorbed water from zeolite beds usually entailsapplying some sort of energy to the beds, such as thermal, infrared, ormicrowave, and purging with a dry gas or applying a vacuum to the bedsduring the regeneration process. These regeneration processes areimpractical in a portable concentrator due to high temperature or highpower requirements. As a result, the accumulation of adsorbed water overtime results in a reduction in capacity of the beds, as fewer sites areavailable for nitrogen binding. Fewer binding sites in the adsorbent bedcan result in a decrease in product purity over time as nitrogen passesthrough the sieve beds and dilutes the oxygen product gas, and shortensthe service life of the concentrator. Many zeolites used in airseparation, and in particular advanced adsorbents, particularly the highlithium containing low silica X type zeolite (LiLSX) used in portableconcentrators, are hydrophilic in their activated state due to theinteraction of the strong dipole moment of water molecules with theelectric fields present in the LiLSX cages and can therefore be prone tothis problem. In the effort to make more compact and efficientconcentrators, PSA cycle frequencies can increase to rates approaching10 cycles per minute and adsorbent productivity increases accordinglywith advances in process and adsorbent technology to productivitiesexceeding 10.0 ml of oxygen per gram of adsorbent. The correspondingdecrease in adsorbent inventory exacerbates the problem as the amount ofgas processed per unit of adsorbent increases proportionally, (the bedsize factor decreases) and the presence of impurities in the process gascan deactivate the adsorbents at a much faster rate than withconventional PSA processes, as described in U.S. Pat. Nos. 7,037,358 and7,160,367, which are incorporated by reference herein.

It is therefore necessary to design portable oxygen concentrators suchthat zeolite contamination can be prevented or handled in a manner thatavoids costly or frequent maintenance by a field technician or equipmentprovider. While the inventors have previously disclosed a system thatachieves long sieve bed life by removing water prior to the feed gascontacting the zeolite in U.S. co-pending application Ser. No.11/998,389, whose teachings are incorporated by reference, this approachadds size and cost to the system to achieve its resistance to zeolitecontamination. It is therefore desirable to design a portable oxygenconcentrator that minimizes size and weight as a function of oxygenoutput with commonly available commercial adsorbents such as Z12-07manufactured by Zeochem or Oxysiv MDX manufactured by UOP. Whileeliminating water removal components such as membrane air dryers orpretreatment layers such as activated alumina or an NaX type zeolitewill reduce the size and weight of the sieve beds it will also reducethe service life of the sieve beds to an unacceptable level. Oxygenequipment used for Long Term Oxygen Therapy (LTOT) is optimally deployedfor 3-5 years without any service requirements. Any service requirementwithin that time interval simply adds to the overall cost of theequipment, which substantially reverses any cost benefit gained byremoving a membrane air dryer or pretreatment layer. Further, allowingsieve bed contamination without prevention or service may lead toproviding 82-87% purity oxygen instead of 87-95% pure oxygen to thepatient. At this time, portable oxygen concentrator adoption willrequire smaller, lighter devices that do not require field service by atechnician or equipment provider, but also minimize size and cost of theequipment.

A typical adsorbent bed or adsorber is constructed of a column with aninlet port and an outlet port arranged at opposite ends. The inlet portis used for admitting pressurized feed gas from the compressor as wellas exhausting the waste gas out of the system in the countercurrent(opposite to the direction of flow of the feed gas) direction. Theoutlet port allows product gas to flow to the accumulator where it canbe delivered to the patient. The outlet port also admits product gasback into the exhausted sieve bed in the countercurrent direction topurge the column of remaining waste gas prior to introducing additionalfeed gas. Inlet and outlet ports must create a sealed connection toallow pressurized feed gas and product gas to pass into and out of thecolumns without wasteful leaks that would upset the balance of thesystem or let oxygen rich product gas escape from the system. The inletand outlet port connections are typically composed of barb fittings,quick connect fittings, tapered pipe thread fittings, or integratedmanifold connections such as adhesives, face seals, gaskets, o-rings orstraight threads. The adsorbers would typically be connected to thevalve manifold of the concentrator through tubing or a direct manifoldconnection. Either prior art construction method resulted in a robustpneumatic connection that was only meant to be disconnected by a trainedservice technician who could access the internal components of theconcentrator and disconnect or disassemble the inlet and outletconnections. Some columns, such as those that are adhesive bonded to anintegrated manifold, may not be removable at all in a field serviceenvironment and must be replaced in combination with other systemcomponents to achieve zeolite replacement.

BRIEF SUMMARY OF THE INVENTION

The invention is a portable oxygen concentrator platform, including aPSA/VPSA/VSA core section capable of mating with user replaceableadsorbers. The core section includes all of the concentratorinstrumentation, mechanics, and pneumatics other than the adsorbers andincludes a housing; a controller; a user interface; at least onecompressor, air control valve, and air filter, comprising a PSA/VPSA/VSAoxygen system when mated with user replaceable adsorbers; and a patientdelivery apparatus. The core also includes at least one adsorberreceptacle that is capable of mating to a user replaceable adsorber. Thereceptacle includes at least two pressure sealed gas connections toinlet and outlet ports of the core section, at least two easilydisconnectable pressure sealed gas connectors for mating to an inlet andoutlet port on a user replaceable adsorber, and a user operable adsorberretention mechanism. Mating a user replaceable adsorber with theadsorber receptacle forms a complete portable oxygen concentrator. Theinvention is applicable to the portable medical concentrator field wherethe concentrator preferably weighs less than 10 pounds, produces lessthan 45 dba acoustic noise when operating, and has an output gas flow of5 lpm or less and has rechargeable battery capable of running theconcentrator for greater than 2 hours. In a preferred embodiment, theconcentrator weighs less than about 8 pounds.

The invention also may be a combination of the platform section and atleast one user replaceable adsorber, forming a complete portableconcentrator. The user replaceable adsorber capable of mating withcompatible portable oxygen concentrator platform includes at least oneselective adsorbent, disconnectable pressure sealed gas connectors formating to the platform receptacle inlet and outlet connectors, andmating retention mechanism to the platform adsorber receptacle retentionmechanism.

In certain embodiments, the battery mounts to the instrumentationsection and prevents removal of the adsorbers while the battery isattached, and there may be a removable case that encloses the platform,user replaceable adsorber beds and battery when all three are mountedtogether.

In other embodiments the inlet and outlet ports may include one or moreradial seals, and the adsorber and receptacle ports insert beyond theradial seal by at least 0.030″. The leak rate of the seals is preferablyless than about 10 SCCM at the maximum rated operating pressure orvacuum level of the adsorber which may be from 0.2 atmospheres to 3.0atmospheres. In certain embodiments the adsorber ports are coaxial withthe receptacle ports.

In some embodiments either the platform or adsorber retention mechanismcomprises a sliding spring loaded plunger and the corresponding matingretention mechanism includes a slot which mates with the plunger. Thespring loaded plunger snaps into the slot when the adsorber is mated tothe platform thereby retaining the adsorber and actuation of the plungerreleases the adsorber. The retention force of the release mechanism ispreferably less than about three pounds, and the plunger may be fingeractuated to release the adsorber.

In other embodiments, either the platform or adsorber retentionmechanism includes a screw operated tab and the corresponding matingretention mechanism includes a slot which mates with the tab. The tab isrotated into the slot when the adsorber is mated to the platform therebyretaining the adsorber and reverse rotation of the tab releases theadsorber.

In other embodiments, the platform retention mechanism includes a pushbutton actuated spring loaded plunger and the adsorber retention matinghardware includes a slot which mates with the plunger. The spring loadedplunger snaps into the slot when the adsorber is mated to the platformthereby retaining the adsorber and push button actuation of the plungerreleases the adsorber. The adsorber is preferably released with lessthan about 25 Newtons of force applied to the push button, and theremovable adsorber mates to the instrument section in an axisperpendicular to the flow of gas through the column.

In preferred embodiments, the adsorber receptacle gas connections areconnected to the air control valves by compliant pressure members. In aparticular version, the adsorber receptacle gas connectors are directlyconnected to the compliant members, and when connected to the compliantmembers, are held in place by a housing mounting element structurallyindependent from the receptacle gas connector. In an alternativeembodiment at least one of the gas connection could be directly to amanifold.

In other embodiments, the platform retention mechanism includes athreaded adsorber and threaded adsorber receptacle. The inlet and outletports may be coaxial and located on one end of the adsorber. Theadsorber or the adsorber receptacle have radial seals that enable thesealing of the gas connection in any rotational orientation around thecenter axis of the adsorber.

In certain embodiments, the adsorbed is retained to the receptacle by atwist to lock mechanism. The twist lock may be engaged by less thanabout 180 degrees of rotation, and the inlet and outlet ports may becoaxial and located on one end of the adsorber.

In other embodiments, the platform retention mechanism includes a hingedcover. The hinged cover snaps into place when the adsorber is mated tothe platform thereby retaining the adsorber, and opening the coverreleases the adsorber. The hinged cover may preferably be disengagedwith less than about 25 Newtons of force and can be operated by afinger.

In other embodiments, one of the inlet or outlet ports is rigidlymounted to the receptacle by any of a twist to lock or threadedengagement and at least one of the inlet of outlet port connections ismade by attaching a flexible tube to the port.

BRIEF DESCRIPTION OF THE DRAWINGS

The understanding of the following detailed description of certainpreferred embodiments of the invention will be facilitated by referringto the accompanying figures.

FIG. 1 shows the general elements of gas concentrators as applicable tocertain embodiments of the invention.

FIG. 2 illustrates the general concept where the concentrator platformis one portion and the user replaceable adsorber is another portion of acomplete concentrator.

FIGS. 3A, and 3B illustrate the concentrator sections in both anunassembled and assembled state.

FIGS. 4A and 4B illustrate an assembled concentrator in a case.

FIGS. 5A and 5B depict an exemplary user replaceable adsorber.

FIGS. 6A, 6B, and 6C depict one example of a suitable user actuatableadsorber retention mechanism.

FIGS. 7A, 7B, 7C, and 7D depict another example of a suitable useractuatable adsorber retention mechanism.

FIG. 8 depicts a port seal for a replaceable adsorber where the port isindependently mounted from the platform chassis.

FIGS. 9A, 9B, 9C and 9D depict another example of a suitable useractuatable adsorber retention mechanism.

FIGS. 10A and 10B depict an alternative port geometry.

FIGS. 11a and 11B depict an arrangement where user replaceable adsorbersare installed with a threaded interface.

FIGS. 12A and 12B depict details of the threaded interface.

FIGS. 13A and 13B depict a twist-lock adsorber interface.

FIGS. 14A, 14B, and 14C depict another example of a suitable useractuatable adsorber retention mechanism.

FIGS. 15A and 15B depict another example of a suitable user actuatableadsorber retention mechanism.

FIGS. 16A and 16B show that alternative inlet and outlet portarrangements are possible.

FIGS. 17A, 17B, 17C, and 17D depict a variety of radial sealarrangements.

FIGS. 18A and 18B show an embodiment where one or more of the gasconnections may be directly to a manifold

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, general features of a portable therapeutic gasconcentrator are shown. Typically gas is drawn into the inlet through aninlet filter 1 into a compressor 2. Compressed air is then delivered ata rate of about 3 LPM to 30 LPM (through various filters and otherdevices) to a gas separation section for selectively adsorbing acomponent of the gas. The preferred embodiments of the invention,although applicable to a variety of gas concentrator implementations,will be described in detail for the case where the inlet gas is air, andthe gas separation section is based on PSA, VSA, VPSA or somecombination thereof, utilizing adsorbent beds 3 which selectively adsorbnitrogen, producing oxygen rich product.

A variety of gas separation section cycle types and bed arrangements areknown in the art, most of which can benefit from the embodiments of theinvention. Whatever the details of the gas separation section 3,typically product gas is accumulated in a storage device 4. Storagedevices may include a tank in the traditional sense, or may be someother device effective for holding a volume of gas, such as a tube, orsome other volume filled with an adsorbent to increase its holdingcapacity or even an empty portion of the adsorber itself at the productend of the adsorber. Many modern concentrators used for therapeuticapplications also include a programmable controller 5 to operate theconcentrator and provide for user interface 8 and communications. Alsotypical are gas exhaust 6, which may have a vacuum applied in the caseof VPSA or VSA systems, and delivery to patient, which often is througha conserver device 7.

Despite the effective moisture mitigative measures described inco-pending application Ser. No. 11/998,389 which might remove 40-98% ofwater molecules from the feed gas stream, some moisture will remain inthe beds 3 when the concentrator is turned off. For the case where thereis a desiccant layer, even for a very dry design, the desiccant existsto remove any remaining water as well as other impurities, such as CO₂,from the feed gas. During operation impurities are not a significantproblem, as the bed 3 is back-purged or evacuated with vacuumperiodically in the Adsorption Cycle, thereby not leaving time formoisture and other impurities to diffuse into adsorbent. When theconcentrator is not running, particularly for a long period of time,there will be a strong driving force to diffuse for any impuritiesadsorbed on the pretreatment layer (or feed end of the bed in the caseof no pretreatment layer used) or in the gas phase in the void space ofthe desiccant/adsorbent at the feed end of the bed. If the concentratoris not sealed to the outer atmosphere via a valve on the exhaustcontaminants can diffuse either to the outer atmosphere (likewise othercontaminants can diffuse into the beds) or the contaminants can diffuseinto the active “clean” section of the bed(s). If the concentrator issealed to the outer atmosphere via a valve, any impurities present willdiffuse into the bed only. Pretreatment layers are often selected due totheir ease of regeneration during process cycles relative to that forthe contaminants in the active separation layer. Thus during shutdownconditions the result can be a material with a low affinity for a givencontaminant adjacent to a material with a high affinity for a givencontaminant, and a large gradient in chemical potential for thecontaminant provided sufficient treatment of the feed gas has takenplace. Given the complex array of components required to prevent thecontamination of zeolite while a portable oxygen concentrator is runningand while it is in storage, the inventors devised a way to treat thesieve beds as a semi-disposable item so that they can be readilyreplaced rather than protected or overdesigned to achieve the requireddevice service life of the system as a whole.

While it is known in the art to make the zeolite beds easily serviced,there have been no successful designs that minimize the number ofreplacement components and simultaneously retain the ability for thepatient to easily change the sieve beds. The invention herein requires aconcentrator to be designed from the ground up around the concept of afield replaceable sieve bed. The sieve beds must be easily removed fromthe system, yet still retain their air-tight sealing mechanisms androbust resistance to shock, drop, and vibration. In medical oxygenconcentrators, and particularly portable oxygen concentrators currentlyin the marketplace, access to the sieve beds typically requires removalof several outer housing components, tubing connections, fittings,screws, and other hardware components. These designs are simplyunsuitable for field service by the user of the oxygen concentrator.

A particularly effective embodiment of the invention is a portableoxygen concentrator where the sieve bed cartridges or adsorbers can beremoved and replaced without removing the outer housing or any fastenersof any kind. FIG. 2 illustrates a preferred embodiment where inlet andoutlet gas connections 201 and 202 are located externally to aconcentrator platform section 20, containing the concentrator elementsother than the adsorber beds, to allow for easy field replacement ofadsorber 21 with inlet and outlet ports 211 and 212 respectively.Further, the adsorbers are robustly attached to core platform 20 towithstand the necessary shock, vibration, and impact a portable oxygenconcentrator may endure via retention mechanism components 203 and 213.By locating the adsorbers 21 outside of the platform 20, the integrityof the concentrator assembly 20 is not compromised by being accessed bythe user who would not have adequate training to perform maintenance oninternal components of the platform 20. The receptacle ports 201 and 202are preferably connected to the air valves by compliant members 9 and10.

A portable concentrator with sieve beds designed for field service issubstantially different than a typical portable oxygen concentrator. Thedesign for patient service changes the layout of the concentrator sothat operational components of the system are accessible to the patientby being located external to the concentrator housing. While this changefacilitates the patient servicing of the system, it also poses aestheticchallenges to the designer since the portable concentrator is usedoutside the home and must not look out of place while being carried by apatient. Therefore, it is an objective of the present invention toseamlessly integrate the adsorbers into the industrial design of theconcentrator so that they remain accessible, but appear to blend in withthe overall design of the concentrator. In a preferred embodiment shownin FIGS. 3A and 3B the adsorbers 21 form the sides of the concentratorwhile the battery 31 forms the bottom of the concentrator. FIGS. 3A and3B further depict a mechanical advantage designed by the inventors touse the mechanically robust battery 31 and battery latching mechanism310 to reinforce the retention of the adsorbers and to preventinadvertent release of the adsorbers during operation. To remove theadsorbers 21 for the purpose of exchanging them, the user would firstremove the battery to access the adsorber release mechanisms 203/213.The entire system 30 is then preferably mounted inside a carrying case40 to enable portable use by the user (FIGS. 4A and 4B).

FIGS. 5A and 5B depict a preferred embodiment of the adsorber designedby the inventors. The adsorber is built as an independent unit and canbe pneumatically interfaced to the platform 20 via inlet and outletports 211 and 212 while being mechanically interfaced to theconcentrator via retention receptacle 214. The internal components ofthe adsorber 21 are similar to other adsorbers found in portable oxygenconcentrators designed by the inventors. The adsorbers contain anitrogen selective adsorbent 219, porous frits 21 d to retain theadsorbent and springs 21 c to prevent the adsorbent from moving andbreaking down during pressure cycling that is typical with a PSA system.The preferred embodiment 21 shows the column cap 21 b being threadedinto the column 21. This embodiment allows the external surfaces of theadsorber to be smooth and free of fasteners or retainers that wouldotherwise pose a hazard to the user while exchanging the adsorbers inthe concentrator. Further, the threaded engagement of the cap to thecolumn ensures that the contaminated adsorbers can be returned to thefactory for replacement of the adsorbent, thus further reducing the costof the adsorber exchange. The cap could alternatively be permanentlyaffixed to the column by rolling the edge of the column over the cap forretention or using adhesive to seal the two parts together, but thesemethods make the adsorber a throw-away item which creates waste. Thepreferred embodiment designed by the inventors allows only the adsorbentor adsorbents to be discarded during an adsorber refurbishment at thefactory.

A further objective of the inventors was to develop an appropriatelatching mechanism that would securely hold the adsorbent vessels sealedto the concentrator, but also allow for easy replacement by the patient.FIGS. 6A, 6B, and 6C depict an exemplary latching mechanism comprised ofa receptacle 214 on the adsorber and a retention plunger 204 on theplatform 20. The latching plunger 204 is held in place by spring forceapplied by spring 204 a. The latch is disengaged by the user by slidingthe engagement button 204 b away from the column latch receptacle 214.The force applied by spring 204 a must be sufficient to preventinadvertent disengagement of the latch, but also low enough to be easilydisengaged by the users finger without a painful or difficult effort onthe part of the user. The inventors have found that a disengagementforce of approximately 10-25 Newtons meets both of these requirements.As shown in the Figures, the location of the mechanisms could beswitched between the adsorber and platform, but it is generallypreferable to keep the cost and complexity as low as possible for thereplaceable adsorber, so the latching hardware on the platform ispreferable.

FIGS. 7A, 7B, 7C, and 7D depict an alternative embodiment of theinvention where the retainer 216 is engaged by locking tab 215 via therotation of locking screw or knob 206. Reverse rotation of the lockingscrew or knob 206 disengages the locking tab 215 allowing the adsorberto be removed. This design includes the advantage of not requiring aspring to maintain the retention of the adsorber, but the rotationaldesign also may require a common tool such as a Phillips screwdriver orTorx driver to remove or install the adsorbers. Requiring a tool forremoval or installation of the adsorbers might be an advantage in someusage scenarios or a disadvantage in other usage scenarios. Theinventors designed the concentrator system to allow for these differingusage scenarios so that the optimal latching and retention mechanismsmay be chosen accordingly. As for the embodiment of FIGS. 6A, 6C, and6D, the placement of the mechanisms could be reversed as shown, but theplacement of the rotating tab on the platform is preferable.

As in any manufacturing operation, there will be variations in thedimensions of all components of the system, so the user replaceableadsorbent must contain a significant amount of sealing overlap toprevent inadvertent leakage that would degrade the system's performance.Referring to FIG. 8, in a particular embodiment, the inlet and outletconnections 211 and 212 must therefore contain overlapping sealingelements that allow for some positional compliance without sacrificingthe quality of the sealing of the pneumatic connections. This compliantsealing mechanism is achieved by using an o-ring on the adsorber and avertical bore 201 a on the receptacle 201 that creates a seal along itsentire length, thus allowing between 1 and 5 millimeters of verticalcompliance to the seal. This compliance allows for some variation andcompliance in the latch as well as some variation in the height of thecolumn components that would be seen in a typical manufacturedcomponent. Further, FIG. 8 depicts the gas receptacle 201 as a modularcomponent that is independent of the platform 20. This is accomplishedby connecting adsorber receptacle port 201 directly to compliant member9, with a locking mechanism 201 b. Thus platform 20 is used to locatethe port 201, but they are not a shared structure. By decoupling thepneumatics from the structural elements of the system, the pneumaticsare protected from the adverse affects of drop or impact. In the extremecase when platform 20 housing components are broken during impact ordrop, port 201 may likely stay connected to member 9 and column inlet oroutlet fitting 212 a. Thus the pneumatic system integrity may bemaintained by adhering to the modular gas connector system 201 and 212as shown in FIG. 8 even in the event of damage to the core system 20.

FIGS. 9A, 9B, 9C, and 9D depict an alternate latching mechanism thatutilizes push button adsorber release buttons 207 to disengage thelatching mechanism 207 b and 207 c and release the adsorbers 21. Again,the spring 207 a must exert an optimal force of about 10 to 25 Newtonson the latching mechanism to sufficiently secure the adsorber 21 duringuse and pressure cycling while still enabling the finger of the user toovercome the spring force and release the adsorber 21 without discomfortor difficulty.

FIGS. 10A and 10B depict another alternate embodiment of the inventionwhere the axis of insertion of the inlet and outlet ports 211 and 212are perpendicular to the axis of flow of gas through the adsorber 21.This embodiment simplifies the design by utilizing the same gasconnections at the inlet and the outlet port, but does not have theadvantage of being able to utilize the battery as a redundant retentionmechanism during use.

The coaxial threaded adsorbers 21 in FIGS. 11A and 11B and FIGS. 12A and12B are another embodiment of the invention where both gas inlet and gasoutlet ports 211 and 212 are coaxial and located at the same end of theadsorber by utilizing an integral return tube to retrieve gas from theopposite end of the column. The engagement and retention threads 217create the mechanically robust connection between adsorber 21 andplatform 20 while the pneumatic connections 211 and 212 are radiallysealed by o-rings with sufficient vertical overlap to allow adsorber 21to seal in any rotational orientation such that rotational position ortiming is independent from the sealing. Adsorber endcap 21 a is threadedonto return tube connection 212 to seal the return tube. Adsorber endcapis then sealed to column 21 c in any rotation by any number of possiblesealing methods such as an o-ring or face seal gasket. The entireadsorber including column 21 c and endcap 21 a then mate to core section20 to form a complete portable oxygen concentrator. The rotationalindependence ensures that user replacement of the adsorber and thevariable tightening torque applied by the user will not createdetrimental leaks at the inlet and outlet gas connections.

The alternate embodiment of the invention depicted in FIGS. 13A and 13Butilize a twist-lock mechanism to lock the adsorber 21 to the platform20. Progressively engaging locking tab 218 draws adsorber 21 into thereceptacle located in platform 20 and is ideally employed in combinationwith the coaxial adsorber design where both inlet and outlet ports 211and 212 are collocated at a single end of the adsorber. Alternatively,one of the inlet or outlet ports may be located at the opposing end ofthe adsorber 21 and the gas connection may be made with a flexibletubing element 10 as depicted in FIGS. 15A and 15B.

Yet another alternate embodiment of the user replaceable adsorber isdepicted in FIGS. 14A, 14B, and 14C. In this embodiment, adsorber 21 isheld in place to platform 20 by a hinged floorplate 209 such that noretention elements at all are required on the adsorber 21. In thisembodiment the hinge 209 a and the latch 209 b are both mounted on theplatform 20 such that floorplate prevents the adsorber from disengagingfrom the platform 20 when latched in the closed position by latch 209 b.

The specific definition of the inlet and outlet ports on adsorber 21 aremerely chosen by convention and can be reversed in any embodiment asdepicted in FIGS. 16A and 16B. A typical adsorber as designed by theinventors utilizes a larger inlet port where feed gas enters the columnto prevent power losses caused by flow restriction and a smaller port onthe product end or outlet where the oxygen exits the adsorber or entersthe adsorber during the purge step of the PSA cycle. In constructing theadsorber, the feed or inlet end of the adsorber may be further definedwhen a layered adsorbent system is utilized and a pretreatment layer isused to remove contaminants from the feed stream prior to the exposingthe main layer adsorbent to the feed stream.

Inlet and outlet ports and receptacles 201 and 211 may utilize a varietyof well established sealing elements as depicted in FIGS. 17A and 17B.Sealing element 17 is ideally a compliant o-ring made from one ofseveral compounds such as rubber, viton, or silicone. Alternately, thesealing element 17 may be a custom face sealing gasket also made ofrubber, viton, or silicone, but this embodiment may lack the necessarycompliance to produce a repeatable and robust seal as part tolerancesvary in a high volume production environment.

Although the preferred approach to connect the adsorber/receptacle portsto the platform internal valving is by compliant member for increasedresistance to shock, it is certainly possible to make one or more theseconnections by having the receptacle ports connect directly to amanifold. Such an arrangement is shown by way of example where one portof adsorber 21 connects directly to manifold 181 as in FIGS. 18A and18B.

The foregoing description of the preferred embodiments of the presentinvention has shown, described and pointed out the fundamental novelfeatures of the invention. It will be understood that various omissions,substitutions, and changes in the form of the detail of the apparatus asillustrated as well as the uses thereof, may be made by those skilled inthe art, without departing from the spirit of the invention.Consequently, the scope of the invention should not be limited to theforegoing discussions, but should be defined by appended claims.

We claim:
 1. A portable oxygen concentrator, comprising: a platform,comprising: a housing, a controller, a user interface, at least onecompressor, air control valve, and air filter, a patient deliveryapparatus, and at least one adsorber receptacle comprising two gasconnector ports; at least one adsorber configured to be userreplaceable, comprising: a column having a top end and a bottom end, thecolumn configured to contain a nitrogen selective adsorbent material,wherein a flow axis of gas through the column is between the top andbottom ends; and a first disconnectable pressure sealed gas connectorand a second disconnectable pressure sealed gas connector disposed onthe top end and the bottom end of the column respectively, each of thefirst disconnectable pressure sealed gas connector and the seconddisconnectable pressure sealed gas connector comprising a central axis,wherein the first disconnectable pressure sealed gas connector and thesecond disconnectable pressure sealed gas connector are in fluidcommunication with the column and extend at least one of in parallel orperpendicularly to the flow axis in the same direction and the centralaxes of the first disconnectable pressure sealed gas connector and thesecond disconnectable pressure sealed gas connector are parallel to eachother; and a retention mechanism configured to be hand operable,comprising an adsorber portion and a mating adsorber receptacle portion;wherein the at least one adsorber is configured to mate with theplatform to form a complete oxygen concentrator; wherein the at leastone adsorber when mated is accessible from the exterior of the platform;wherein the retention mechanism is accessible on the exterior of theplatform; and wherein the portable oxygen concentrator weighs less than10 pounds, produces less than 45 decibels acoustic noise when operating,and has an output gas flow of 5 liters per minute or less and has arechargeable battery capable of running the portable oxygen concentratorfor greater than 2 hours.
 2. The portable oxygen concentrator of claim1, wherein the portable oxygen concentrator weighs less than 8 pounds.3. The portable oxygen concentrator of claim 1, wherein the portableoxygen concentrator weighs less than 4 pounds.
 4. The portable oxygenconcentrator of claim 1, wherein the rechargeable battery is configuredto mount to an instrumentation section and prevents removal of the atleast one adsorber while the rechargeable battery is attached.
 5. Theportable oxygen concentrator of claim 4, wherein the rechargeablebattery is configured to mount to the instrumentation section andprevents removal of the at least one adsorber while the rechargeablebattery is attached by blocking the retention mechanism.
 6. The portableoxygen concentrator of claim 1, wherein at least one of the firstdisconnectable pressure sealed gas connector and the seconddisconnectable pressure sealed gas connector inserts beyond an adsorberradial seal by at least 0.030 inches.
 7. The portable oxygenconcentrator of claim 1, wherein at least one of the firstdisconnectable pressure sealed gas connector and the seconddisconnectable pressure sealed gas connector contains at least oneradial seal.
 8. The portable oxygen concentrator of claim 1, wherein theleak rate of the gas connector ports is less than 10 Standard CubicCentimeters per Minute at a maximum rated operating pressure of the atleast one adsorber.
 9. The portable oxygen concentrator of claim 1,wherein the adsorber portion of the retention mechanism comprises aplunger and the adsorber receptacle portion of the retention mechanismcomprises a receptacle which mates with the plunger, wherein the plungerengages the receptacle when the at least one adsorber is mated to the atleast one adsorber receptacle thereby retaining the at least oneadsorber.
 10. The portable oxygen concentrator of claim 9, wherein theplunger is spring loaded and actuation of the spring loaded plungerreleases the at least one adsorber.
 11. The portable oxygen concentratorof claim 10, wherein an actuation force of the spring loaded plunger isless than 3 pounds.
 12. The portable oxygen concentrator of claim 11,wherein the spring loaded plunger is finger actuated to release the atleast one adsorber.
 13. The portable oxygen concentrator of claim 9,wherein the plunger is finger actuated.
 14. The portable oxygenconcentrator of claim 1, wherein at least one of the adsorber receptaclegas connector ports is directly connected to air control valves on amanifold.
 15. The portable oxygen concentrator of claim 1, wherein thefirst disconnectable pressure sealed gas connector and the seconddisconnectable pressure sealed gas connector are sealed by o-ring seals.16. The portable oxygen concentrator of claim 1, wherein the at leastone adsorber comprises a plurality of adsorbers, wherein each adsorberof the plurality of adsorbers is individually releasable.
 17. Theportable oxygen concentrator of claim 1, wherein an adsorber cap isthreaded to the column of the at least one adsorber.
 18. The portableoxygen concentrator of claim 1, wherein the adsorber portion of theretention mechanism is located on the at least one adsorber and theadsorber receptacle portion of the retention mechanism is located on theplatform.
 19. The portable oxygen concentrator of claim 1, wherein theat least one adsorber comprises a feed port and a product end port,wherein the feed port is larger than the product end port.
 20. Theportable oxygen concentrator of claim 1, wherein the at least oneadsorber contains a layered adsorbent system.